This invention relates to a coupler for hitching a trailing vehicle to the spherical ballhead of a towing vehicle. More particularly, the invention relates to a coupler of the same general type as the coupler disclosed in Kirk et al U.S. Pat. No. 3,163,445.
Such a coupler includes a body whose forward end is formed with a downwardly opening socket for receiving the ballhead. The rear side of the socket is open and is adapted to be closed by a ball clamp which is supported on the coupler body to move back and forth between clamped and released positions. In its clamped position, the clamp engages the ball to lock the latter in the socket while still permitting relative turning and pivotal movement between the ball and the socket.
As a result of being supported to move back and forth relative to the body, the ball clamp also is capable of pivoting relative to the body about a transversely extending axis. In order to enable the ball clamp to properly engage the ball, it is necessary to locate the clamp in a predetermined angular position during assembly of the clamp and the body and to hold the clamp in such position over the service life of the coupler.
In the coupler disclosed in the Kirk et al patent, the ball clamp is located and then held in a predetermined angular position by a cam member located between the upper side of the ball clamp and a rearwardly and upwardly inclined upper wall of the coupler body. The cam member is supported by a bolt-and-slot connection which permits adjustment of the cam member and thus adjustment of the angular position of the clamp as wear occurs between the mating faces of the clamp and the ball.
Experience has shown that an adjustable connection between the cam member and the coupler body is not desirable since such a connection might result in the angular position of the ball clamp being improperly adjusted after the coupler has left the manufacturing facility. To avoid this, more recent couplers of the Kirk et al type has been manufactured with the cam member welded rigidly to the body after first having been located in the proper position. Welding of the cam member, however, is not easily achieved and, more importantly, it is difficult with mass production inspection techniques to verify that an adequate weld has been established.
A coupler of the type disclosed in the Kirk et al patent also includes a pivoted yoke for locking the ball clamp in its clamped position and for releasing the ball clamp for movement to its released position. The yoke includes a pair of transversely spaced arms which straddle the coupler body and also includes a pair of transversely spaced ears which straddle a latch for controlling the position of the yoke. The connection between the ears and the arms of the yoke is relatively weak and sometimes leads to failure of the coupler under extreme load conditions.